Adjust with allen key (#2).
Adjust with allen key (#3).
Adjust with allen key (#4).
Turn allen key (#1) clockwise to increase weight.
Using thin allen wrench or pin through hole, trigger stop behind trigger may be screwed in or out (as shown in diagram).
For newer models, turn allen key set in trigger shoe clockwise until trigger will not release, then back off one quarter turn (not shown in diagram).